Little help on dating older carrier forced gas air furnaces

I am getting conflicting information on the dates of older carrier units. We just did a large commercial building with 24 80,000 BTU furnaces in the individual suites. Can somebody give me a little help in dating them, here are two examples:

Q1A46849 I think this is 1991?
R1A58163 I think this is 1981?
X1A01921 I think this is 1971?

Thank you in advance for any help you can provide here.

Rick Moore
Sherlock Homes Inspection & Appraisal, LLC
Mead, CO

I believe those are all 1981. Reference is from Style 3 at

I agree with James, all 1981.

You are correct I missed that one when looking at building intelligence center this morning. Thank you.


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